The invention concerns an individual wheel drive with a rear-mounted planetary gear for motor vehicles. Individual wheel drives with rear-mounted planetary gear are known already, an example of such an individual wheel drive being given in German Patent No. 26 30 206.
Those individual wheel drives with a rear-mounted planetary gear can be used, for example, in short-distance buses. Since, in this transmission system, the otherwise usual axle-beam housing for an axle input and a differential are eliminated, it is possible to build buses with a very low floor level. In the former, driving drafts for low-floor buses with individual wheel drives, the size of the prime mover and of the actuating devices for the brake are disadvantageous since they make large wheel wells necessary and narrow down the passage into the floor of the bus to the height of the wheels. For optimally building the body of a vehicle in accordance with the work space, it can prove necessary to fit the primary mover or a bunched up transmission system of several engines offset relative to the wheel axle.
The problem on which the invention is based is to provide an individual wheel drive with a rear-mounted planetary gear which, as a result of the drive unit being fitted offset relative to the wheel axle, makes an optimal use of the interior of the vehicle possible and in which said axle offset is compensated in the planetary gear.
This problem is solved by an individual wheel drive according to the preamble of the main claim and having the characteristic features thereof.
According to the invention, the individual wheel drive for a vehicle comprises at least one planetary gear with one sun gear, one ring gear and one planet carrier. The ring gear drives a wheel hub on which is fastened a single or dual wheels. Wheel bearings rotatably support said wheel hub. The individual wheel drive, according to the invention, in addition comprises one brake, one brake caliper and one brake-actuating device. A prime mover or a bunched up input of several engines produces the input power. The shaft of the prime mover or of the bunched up input by several engines is offset with respect to the wheel axle in order to design optimally the whole space required by the input and the brake-actuating device so that the wheel well affects the interior of the vehicle as little as possible. Said axle offset is again compensated in the planetary gear by offsetting the axle of the sun gear from that of the ring gear 15 and planet carrier 16 respectively. The axle of the ring gear coincides with the wheel hub and thus with the wheel axle.
In an advantageous development of the invention, planetary wheels of different diameters grip the sun gear and the ring gear. An offset between the axles of sun gear and the ring gear and planet carrier respectively thereby results. Said planetary gear can have, for example, two planetary wheels of different diameters. In another embodiment, it contains three planetary wheels of different diameters. From a technically logical point of view, said embodiment is, of course, possible only for a small axle offset. At the same time, in a symmetrical arrangement, two of the three planetary wheels can have the same diameter. Embodiments with more than three planetary wheels are also conceivable.
In this individual wheel drive the input is preferably electric. A possible use is in driven rear wheels combined with rigid axle systems for dual or single tires.
In an advantageous embodiment of the invention, the input power of a large electromotor is distributed over several smaller ones. Their respective input power is concentrated by a spur-gear collective drive. The individual, smaller electromotors are axially short so that the whole driving unit projects less in the direction of the interior of the bus. The through width of the interior of the vehicle is thus increased to the height of the wheels with the same total width of the vehicle. The adaptation to the required wheel torque and the wheel speed is effected by the rear-mounted planetary gear. The spur gear of the spur-gear collective drive on the output side is preferably connected with the sun gear of the planetary gear by a gear intermediate shaft. The wheel bearing, which rotatably supports the wheel hub, is advantageously situated between the spur-gear collective drive and the planetary gear. The rims are secured to the wheel hub.
The prime mover(s) are preferably cooled by air, water, oil or other means.
In an advantageous design of the invention, an input from several engines can be separately controlled. This makes possible a greater effectiveness in the intermediate load area in comparison with a one-engine individual wheel drive. The distribution of the input power of the individual wheel drive over several engines of less power which are made shorter than engines of stronger power offers, together with the reduction of the total length of the individual wheel drive, still other advantages: in the case of failure of a prime mover in the wheel head, operation via the remaining engines is still possible. In addition, advantages in cost result by using engines which are in the performance class of prime movers of passenger cars and can thereby be mass produced.
In an advantageous development of the invention, the brake of the individual wheel drive is designed as a pneumatically or hydraulically actuated disc brake and, in the same manner, acts as a service, parking, emergency or auxiliary brake.
The brake caliper is preferably placed beneath the horizontal central line of the wheel. It is advantageously in a circular section between 150xc2x0 and 210xc2x0, the normal vector of the circular disc pointing in the direction of the wheel axle and the angle being measured by the radius vector pointing vertically upward, that is, in direction of the vehicle vertical axle. The brake-actuating device is here designed as a combined diaphragm and spring-accumulator cylinder. It is situated in a hollow axle body in an axle direction. The assembled wheel head is protected against impact by its position within the hollow axle body.
The parking brake advantageously has an emergency release device which is accessible from below through a handhole in the axle body. In the case of failure of the vehicle""s own pressurized air, said emergency release device must be used in order to render towing of the vehicle possible.